[PATCH] selection: send selection events to all connected clients

[Yichao Yu]

A lot of useful features require clipboard access and monitoring
without having a keyboard focus, e.g. clipboard action (klipper[1] and
some download agents), command line access (IPython's %paste magic).
This patch sends out selection events to all clients when the
selection owner changes no matter whether the client has a focus or
not in order to support these features.

[1] http://userbase.kde.org/Klipper
[2] http://ipython.org/ipython-doc/dev/interactive/tutorial.html